Fluid responsive electric switch



May 6, 19469 Filed Jan. 20. 1967 G. WINTRISS FLUID RESPONSIVE AELECTRIC SWITCH Sheet l 20) F164( U- 3o INVENTO ATTORNEYS.

May 6, I969 G. WINTRlss 3,443,044

FLUID RESPONSIVE ELECTRIC SWITCH Filed Jan. 2o. 19e? sheet 2 of 2 ATTORNEYS.

IUnited States Patent vO Int. Cl. H01h 35/24 U.S. Cl. 20.0-83 n v 21 Claims ABSTRACT F THE DISCLOSURE `This invention relates to an electric switch having a diaphragm that divides the interior of the housing into-a pressure chamber'and a switch chamber. F1uid,lsuch as compressed air, is supplied to the pressure chamber and thereis an outlet passage from which the fluid bleeds from the housing unless the ow is totally obstructed. Obstruction of the ow, or release of pressure when the ow has been obstructed, produces a shock wave in the uid 'suicient to operate the switch. The operation is substantially instantaneous and it is not necessary to wait for a mass of lluid to tlow into or out of the chamber.

The pressure of iluid under the diaphragm is adjusted with respectl to a spring in the switch chamber to obtain a degree of overbalance, and this overbalance is reversed by a shock wave in the fluid. There are specific improvements in the switch itself for yadapting it to shock wave operation and for giving it an extremely long life.

The invention is an improved electric switch responsive to changes in tluid flow. An obstruction, or change in obstruction, or a release of the obstruction to lluid flow, produces a shock wave in the iluid column and this wave actuates the switch. The expression shock wave is used herein in a broader sense than in the aircraft industry and is used to designate any rarefaction or positive pressure wave thattravels through a column of'tluid as a dynamic wave, as opposed to changes in the static pressure which occur on a more permanent basis `as the result of owlof masses of fluid into and out of an enclosed space. When used at slow speeds, there are pressure changes resulting'from ow of air into or out of the operating fluid chamber.

1- The invention also includes combinations of the switch with `other apparatus that produces the'waves, such as a cam, a work piece passing along a discharge path, a tank: with liquid at a level below which the liquid should not be'I allowed to fall, and machines that have cyclically moving parts. Such systems may operatethe switch to energize an alarm or a controller.

The switch of this invention includes a housing which is divided into two chambers by a movable wall, preferably a flexible diaphragm. The switch is in one chamber and fluid under pressure is admitted to the other chamber. Resilient means, such as a spring means in the switch chamber, are preferably used to press the diaphragm in one direction, and the fluid pressure reacts against the other side of the diaphragm in a direction opposite to the force of the spring means. By adjusting the pressure, a conditionis obtained with the force on one side of the diaphragm overbalancing the force on the other side, and with the force so correlated that a shock wave in the uid changes the balance the other way to open the switch if it were closed, and vice versa.

i There are various features in the constructionof the switch for adapating it to the intended use and for obtaining substantially instantaneous operation and extremely long life. In practice, the switch has been used with repetitive operations of 240 per second without detectable bounce. One construction with a ball valve element for totally obstructing the ow has Ibeen operated with a valve movement of only .0005 inch.

In describing obstruction to a uid'tlow, the term is used herein to designate a total blockage of the ow, or a partial blockage, or a deflection of ilow that causes a shock wave to travel back up the stream of uid upon initiation of the deection.

, 4Other features of the switch construction relate to the contacts, including relatively fixed contact means consisting of a plurality of balls in la holder and at substantially equal angularly spaced locations around the axis of the switch, -but with the diierent balls at different radial distances from the switch axis; There are also novel constructions for connecting different balls of the relatively fixed contact means with prongs that are the external conductors or lterminals by which the switch is connected in a circuit in which it is to be used. Y v

Other objects, -featuresvand advantages of the invention will appear or be pointed out as the description proceeds.

BRIEF DESCRIPTION OF THE DRAWING In the drawing, forming a part hereof, in which like reference characters indicate corresponding parts in all the views:

FIGURE l is a vertical sectional view of a switch made in accordance with this invention;

FIGURES 2 and 3 are sectional views, on a reduced scale, taken on the lines 2-2 and 3-3, respectively, of FIGURE 1;

FIGURE 4 is a side elevation showing the way in which the switch of FIGURE 1 can be combined with other switches;

FIGURE 5 is a diagrammatic view showing a switch, similar to FIGURE l, but without any valve in the housing for controlling the bleed of iluid from the housing; i

FIGURE l6 is a view similar to FIGURE 5 but showing the switch of FIGURE 1;

FIGURE 7 is a diagrammatic view showing the switch of FIGURE 5 combined with a delivery table along which work pieces travel and with means for actuating the switch in response to the movement of the work pieces;

FIGURE 8 shows the switch of FIGURE 5 combined with means `for detecting the termination or irregularities in the movement of a web;

FIGURE 9 shows the switch of FIGURE 5 combined with a tank and with means for operating the switch in response to a drop in the liquid below a given level in the tank; and

FIGURE 10 is a diagrammatic view showing the switch of FIGURE 5 combined withv a ram of a repetitively operating press. l

DETAILED DESCRIPTION OF THE INVENTION The switch shown in FIGURE 1 includes a housing 20 'l which is divided into two chambers by a movable wall consisting of a tlexible diaphragm 22. This diaphragm is preferably made of rubber or similar plastic material and is preferably reinforced with a web, such as a nylon web. A hardness of 60 durometer has been found satisfactory in practice. Below the ldiaphragm 22 there is a' pressure chamber 24, and'there is an outlet passage 26 leading downward from the pressure chamber 24 to a valve chamber 28. A ball valve element 30, in the valve chamber 28, closes against a seat 32 at the lower part of the valve chamber. l

When the ball valve element 30 is in contact with the seat 32, it totally obstructs flow of Huid from the valve chamber 28 through a discharge opening 34 in the bottom of the valve chamber 28. The valve chamber 28 constitutes part of the outlet passage 26; and both the passage 26 and the valve chamber 28 are, in effect, part of the pressure chamber 24 under the diaphragm 22.

The outlet rpassage 26 has an offset portion 36 through which it communicates with the valve chamber 28. This makes the huid enter the valve chamber 28 at a location which is unsymmetrical with respect to the top surface of the ball valve 30, and is desirable in order to make the ball valve 30 close quickly when a force displacing it has been withdrawn.

FIGURE 1 shows a cam 38 which rotates under the ball valve 30 and which'has a raised portion 40 that contacts with the valve element 30 to lift the valve element frornthe seat 32 with each revolution of the cam 38.

Fluid is supplied to the pressure chamber 24 through an inlet passage 44. This inlet passage 44 communicates with an inlet fitting 46 threaded into a counterbore 48 in one side of the housing 20. There is a filter 50 held against the end of the counterbore by the fitting 46.

A source 52 of fluid at superatmospheric pressure is shown diagrammatically in FIGURE l; and this source 52 is connected with the fitting 46 by piping 54 in series with an adjustable pressure regulator 56.

As long as the valve 30 is in closed position, fluid in the pressure chamber 24 builds up slowly to the delivery pressure of the regulator 56, or remains at that pressure. When the regulator 56 is adjusted to obtain a fluid pressure under the diaphragm 22 greater than the pressure above the diaphragm, a switch above the diaphragm is held in closed position. The downward pressure on the diaphragm 22 is exerted by a spring 58, the operationof f which will be described in connection with the switch.

The spring 58 has a very low spring rate in that the pressure which it exterts is substantially the same whether the switch is open or closed. Because of this low spring rate and the flexibility of the diaphragm 22, wear of the contact surfaces does not have any substantial effect on contact pressure. Even with large dimensional changing resulting from contact wear, the diaphragm 22 merely moves up further and the spring 58 presses the contacts together with substantially the same force as when the contacts were in their original condition.

Whenever the valve element 30 is displaced from itS seat 32 a shock wave travels up the column of fluid in the housing 20 below the diaphragm 22. This shock wave includes a rarefaction wave which permits the spring 58 above the diaphragm 22 to temporarily overcome the force of the fluid pressure below the diaphragm so that the diaphragm moves downward and permits the switch above it to open, in a manner which will be explained later.

Above the diaphragm 22 there is a switch chamber 64 and in this chamber 64 there is a ball holder 66 with openings 68 for holding balls 70 which constitute relatively fixed contacts of a switch. The ball holder 66 fits tightly into the housing 20 with a press t; and the lower part of the ball holder 66 clamps the peripheral edges of the diaphragm 22 against a shoulder in the housing and preferably against a ridge 74 projecting upwardly from the shoulder. The ball holder 66 is made of electrical insulating material and the balls 70 t into the openings 68 with a press lit. The upper ends of these openings 68 are substantially cylindrical but the lower portions of the openings 68 have inwardly curving walls which provide shoulders 76 having substantially the same surface curvature as the balls 70. These shoulders 76 limit the extent to which the balls 70 can be pressed down into the openings 68.

The lower ends of the openings 68, beyond the shoulders 76, are open so that the bals 70 project beyond the openings 68 and into position to contact with a movable contact element 80 which has an annular ridge 82 for Contact with the balls 70. The movable contact element 80 is preferably made of hardened steel and at least the surface of the ridge 82 is silver-plated. The balls 70 are also preferably silver-plated.

A cup 86 is located on top of the diaphragm 22 and is rigidly connected to the diaphragm 22 by a fastening 88 which extends through the diaphragm 22 and which has a head or ange on the under side of the diaphragm. This fastening 88 can be a rivet. The outside diameter of the cup 86 is substantially less than that of the surface of the diaphragm 22 which is exposed inside the lower clamping face of the ball holder 66. This leaves a portion of the diaphragm 22 free to flex and to obtain the necessary movement for operation of the switch. In the illustrated construction, there is a exible annular washer 88 of Mylar or other material which is unaffected by ozone. This washer 88 extends between the clamping face of the ball holder 66 and the top surface of the diaphragm 22 and extends inward under the cup 86 so that all portions of the diaphragm 22, which are exposed to the atmosphere in the switch chamber 64, are protected from any ozone generated by arcing of the switch contacts.

A disc 90 is held in the cup 86 and this disc is thick enough to extend a slight distance above the Icup 86. The disc 90 is made of slippery material, such as glass or Teflon. The movable contact element rests on the disc and is free to slide transversely on the top surface of the disc 90. However, the contact element 80 is held in a centered position by the spring 58 which fits into a recess formed in the top of the contact element 80 by the ridge 82. The upper end of the spring 58 fits around a protuberance 92 at the center of the ball holder 66; and the spring 58 is preferably a conical, helical spring so as to act more effectively in holding the contact element 80 centered.

The openings 68 are preferably located at equal angular spacing about the axis of the switch chamber. This is shown clearly in FIGURE 3 where the axis of the switch chamber is designated by the reference character 94. The highest part of the curved top surface of the ridge 82 is shown in dotted lines in FIGURE 3 andv designated by the reference character 96. This high line is under theV center of one of the balls 70 but it is radially inward of the downwardly projected center of one of the other balls and radially outward of the downwardly projected center of the third ball 70. Thus when the movable contact element 80 (FIGURE 1) moves upwardly, it contacts first with the ball 70 which has its center over the highest part of the ridge 82. Contact of the element 80 with this ball stops further upward movement of the element 80 until the pressure under the diaphragm 22 increases sufficiently to distort the diaphragm 22 and to swing the movable contact element about its point of contact with the first ball as a fulcrum. This further movement of the movable contact element brings it into contact with another one of the balls. Further movement is vabout an axis connecting the points of contact of the element 80 with the first two balls, and this further movement brings the element 80 into contact with the third ball 70. It is not necessary, however, for the con tact element to touch more than two of the balls in order to close the switch.

An insulated partition extends across the tops of the balls 70 and seats against a shoulder 102 in the housing 20. This partition 100 is clamped in position by an upper end 103 of the housing which fits into the lower part of the housing with a press fit and which is permanently secured to the housing by a turned-in edge 106 of the lower part of the housing. There are two helical springs 108 and 110 in the upper part of the housing. The inside diameter of the spring 108 is substantially larger than the outside diameter of the spring 110 and there is a sleeve 112 of electrical insulating material in the space between the springs 108 and 110. An opening 116 in the partition 100 permits the spring 108 to touch one of the balls 70 but the partition 100 prevents the spring 108 from touching the ball 70 which constitutes the other side of the switch circuit, i.e., the right-hand ball 70 of FIGURE 1.

An opening 118 in the partition 100 permits the inner spring 110 to touch the right-hand ball 70 but prevents this inner spring from touching the left-hand ball. The third ball 70 is not in the circuit. Although the drawing shows the right-hand ball 70, which is centered over the high line of the ridge 82, as part of the switch circuit, this ball can be used for support only and the other two balls can be made the conductors of the switch.

The upper end of the housing 20 is closed by a plug 120. This plug is made of electrical insulating material and is held in place by a pin 122. A terminal prong 126 extends through the plug 120 and has a lower portion 128 which extends through an opening in a'separator 130 and into contact with the spring 110. Another terminal prong 136 extends through the insulation plug 120 and has a lower portion 138 which extends through an opening in the separator 130 and into contact with the tOP` of the spring 108. The terminal prongs 126 and 136 are securely held in the insulation plug 120; and the separator 130, which is also made of insulating material, is clamped against a shoulder 140 by the insulation plug 120.

The embodiment of the invention shown in FIGURE 1 has the valve element 30 for totally obstructing the flow of fluid from the housing at certain times; but `for many `applications of the invention, it is more desirable to permit fluid to bleed from the lower end of the outlet passage 26 continuously and to operate the switch by partially obstructing this flow to produce a shock wave. When the invention is used with a continuous bleed of fluid from the housing, the lower end of the outlet passage can be made of any reduced diameter necessary to prevent excessive use of fluid and to maintain some pressure in the. housing under the diaphragm.

The housing 20 has provision for connecting a number of switches in parallel, there being a second threaded counterbore 144 on the side of the housing opposite the counterbore 48. When only Ione switch is in use this counterbore 144 is closed by a plug 146, but when several switches are to be used together, the plug 146 is removed and the housing 20 is connected with a similar housing 20a by a nipple or coupling 148. Similarly, the housing 20a can -be connected with another housing 20b by a nipple or coupling 148'. The switch 20 has the ball valve 30, but the switches 20a and 20b are shown with reduceddiameter orifices 150 in place of a valve element.

FIGURE 5 shows the switch housing 20a supplied with fluid Vunder pressure through a pressure regulator 56, with agauge 154. Flow of fluid from the orifices 150 is obstructed cyclically by a high segment 156 or a cam 158. This cam rotates in timed relation with the apparatus which is to -be controlled by the switch in the housing 20a.

FIGURE 6 is a side elevation of the housing 20 with the cam 38 having its raised section 40 for operating the ball valve element 30 in the manner previously described.

FIGURE 7 shows the switch housing 20a turned upside-down from its position shown in FIGURE 5 and with its orifices 150 opening through an outlet 160 in a delivery table 162 of an automatic machine. Work pieces 164, delivered by the machine, pass across the opening 160 and across an 4opening 160'. The opening 160 communicates through piping 166 with another switch, similar to the switch in the housing 20a; and passage of the work piece 164 across either or both of the openings 160 and 160 obstructs flow of air and produces a shock Wave to operate the switches which bleed though the respective openings 160 and 160".

FIGURE 8 shows the switch housing 20a with its bleed orifices 150 discharging through piping 170 which leads to a discharge -outlet 172 in a block 174 located at the edge of a traveling web 176. This web 176 travels in a direction perpendicular to the paper in FIGURE 8. Termination of the web, or a buckle in the web, or va transverse shifting of the web, change the degree of obstruction of the outlet 172 and produces a shock wave t-o operate the switch in the housing 20a.

FIUGRE 9 shows the switch housing 20a with its bleed orifice connected with a discharge tube 180 extending down into a tank 182. When liquid 1-84 in the tank 182 rises to the lower end of the piping 180, the liquid obstructs the flow of fluid from the orifice 150 `and produces a shock wave to operate the switch in the housing 20a. Similarly, a drop in the liquid level below the end of the piping 180, removes the obstruction, again to operate the switch.

FIGURE 10 shows the switch housing 20a with its discharge orifice 150 connected with piping 190 which has has two branches 191 and 192. Each of these branches 191 and 192 terminates near the end of a surface 194 of a reciprocating element of a repetitive machine, such as a ram 196 of a press. The discharge ends of the branch pipes 191 and 192 are located so that both of them are obstructed when the ram 196 is at one position of its stroke. When it moves downward, the obstruction of flow from the pipe 191 is changed and when the ram moves upward from the position shown in FIGURE 10, the obstruction from the pipe 192 is changed, though the obstruction from the pipe 191 remains the same.

The preferred embodiments of the invention have been illustrated and described, but changes and modifications can be made and some features can be used in different combinations without departing from the invention as defined in the claims.

What is claimed is:

1. A fluid wave-responsive switch including a housing, a movable wall dividing the interior of the housing into two chambers including a switch chamber and a pressure chamber, the movable wall having a center region extending over most of the area of the wall continuously exposed to operating pressure in said pressure chamber, an inlet passage for supplying fluid under pressure to said pressure chamber, an outlet passage from which fluid escapes from said pressure chamber at a predetermined rate when the flow from the outlet passage is unobstructed, a switch in the switch chamber including relatively fixed and movable contact means, Ithe latter being operably connected with the movable wall, resilient means urging movement of the movable contact means and the wall in a direction opposite to that in which the pressure in said pressure chamber urges the wall to move, and means for correlating the force of the resilient means with that of the pressure and volume in the pressure chamber to ycause operation of the switch by a shock wave in the fluid of the pressure chamber when there is a change in the freedom of flow of the fluid.

2. The switch described in claim 1 characterized by said means for correlating including apparatus for sup plying the fluid to the pressure chamber ata controlled rate and pressure, the resilient means being of a strength to exert a force on the movable wall that overbalances the force of the fluid in the pressure chamber to open the switch when the fluid is bleeding from the outlet passage, the overbalance being so limited that a shock wave produced by the fluid in the pressure chamber by a substantial obstruction of the -outlet passage, downstream from the communication of the inlet passage with the pressure chamber, moves the movable wall to close the switch.

3. The switch described in claim 1 characterized by means that obstructs the flow of fluid from the outlet passage, the obstructing means being located out of the path of flow of fluid supplied to the pressure chamber, means for supplying the fluid to the pressure chamber at a controlled pressure that overbalances the resilient means and holds the switch closed while the flow from the outlet passage is obstructed, the resilient means being ofA sucient strength to open the switch when a rarefaction shock wave is produced in the pressure chamber by a release of fluid from the outlet passage as the result of movement, into a less obstructive position, of the meansl that obstruct the flow of uid from the outlet passage.

4. The switch described in claim 3 characterized by the means that obstructs the flow of fluid including a valve element movable between open and closed positions and that has a portion of its length projecting beyond the end of the outlet passage to a location where it can be struck by a high part of a cam for moving the valve element into an open position where it is in inoperative to prevent the ow of fluid from the outlet passage.

5. The switch described in claim 4 characterized by the valve element being a ball, and the outlet passage having a valve seat near its downstream end against which the ball seats under force of the fluid in the outlet passage, said ball being free to rotate when operated by a cam to seat the ball on different areas of its surface at different times and thereby distribute wear.

6. The switch described in claim 5 characterized by the outlet passage having an enlarged lower portion which provides a chamber for holding the valve element, the upper portion of the outlet passage opening into the enlarged lower passage at a location unsymmetrical with respect to the confronting surface of the ball whereby the Itiuid owing downward across the ball, when the latter is lifted from the seat, strikes the ball on one side of the high part of the ball.

7. The switch described in claim 1 characterized by the means for correlating including an element movable to change the rate of said ow from the outlet passage, means for supplying fluid to the pressure chamber and outlet passage, the uid supply means being adjustable to change the pressure and rate of supply to a valve whereby the variations in flow of iluid from the outlet passage open and close the switch in response to shock waves in the iluid produced by the operation of the movable element in changing the flow rate from the outlet passage.

8. The switch described in claim 7 characterized by the movable element being a wheel that rotates with a portion of its surface close to the downstream end of the outlet passage, said portion of the surface of the wheel being of irregular contour so that parts of the surface of the wheel approach closer to the outlet passage than do other parts to change the degree of obstruction of nid ilow resulting from the presence of the wheel.

9. The switch described in claim 7 characterized by the downstream end of the outlet passage being located along a path of movement of workpieces, and a workpiece that crosses the outlet passage to obstruct the iiow of fluid from the outlet passage.

10. The switch described in claim 7 characterized by the downstream end of the outlet passage being in position to be obsrtucted by a web, and a web that moves along a path and that obstructs ow of uid from the outlet passage while the web continues to move along said path.

'11. The switch described in claim 7 characterized by the switch being in combination with a tank for holding liquid, the downstream end of the outlet passage being in position to be obstructed by liquid in the tank when the liquid is above a predetermined level in the tank.

12. The switch described in claim 7 characterized by the switch being combined with a reciprocating machine that has a part with a surface of a given length extending parallel to the direction of movement of that part, the discharge end of the outlet passage being located along the path of movement of said part and in a position that is beyond the part when said part is at one end of its stroke.

13. The switch described in claim 12 characterized by the outlet passage being branched and having two downstream ends located at different points along the path of movement of said part of the reciprocating machine, both of said downstream ends being located in position to be obstructed by the part for one position of the part in its stroke, but each of said downstream ends being located near an opposite end of said surface when the part is in position to obstruct both discharge ends of the outlet passage simultaneously.

.14. An electric switch including a housing, a movable Wall dividing the interior of the housing into Ytwo chambers including a switch chamber and a pressure charnber, an inlet passage for supplying lluid under pressure to said pressure chamber, an outlet passage from which fluid escapes from the pressure chamber at a predetermined rate when the `outlet passage is unobstructed, a switch in the switch chamber including relatively lixed and movable contact means, the latter being operably corinected with the movable wall, and resilient means urging movement of the movable contact means and the wall in a direction opposite to that in which the pressure in said pressure chamber urges the movable wall to move, the movable contact means including a movable contact that moves with the movable wall, the relatively fixed contact means including a plurality of spherical surfaces at angularly spaced locations around the longitudinal axis of the switch in position to be touched by slight movement of the movable contact when the movable wall is displaced toward said spherical surfaces, means exerting opposing forces for moving the movable contact toward and from the spherical surfaces, said means being correlated to bring the opposing forces near enough to balance to move the movable wall in response to a surge of pressure in the fluid, and a holder for retaining the spherical surfaces in position in the switch chamber.'

15. The switch described in claim 14 characterized by the spherical surfaces being at different radial distances from the axis of the switch but all of said spherical surfaces being at substantially the same axial distance from the movable wall, a circular ridge on the side of the movable contact that confronts the spherical surfaces, said ridge being substantially concentric with the axis of the switch and having a substantially circular line at the highest part of the ridge under the center of one of the spherical surfaces, and with the centers of the other spherical surfaces radially inward and radially outward, respectively, of the highest part of the ridge, the movable element having freedom of movement in a plane transverse of the axis of the switch whereby the surface of the movable element slides on the surface of the spherical surfaces to obtain a wiping action of the contact surfaces.

y16. The switch described in claim 15 characterized by there being three spherical surfaces at equal angular spacing around the axis of the switch, the spherical surface holder having openings for receiving the respective spherical surfaces and each of the openings having a shoulder that limits the extent to which the spherical surface can be inserted into the opening, and each of the openings beyond the shoulder being of reduced cross section to the end of the opening nearest to the movable contact, each of said spherical surfaces having a portion of its surface extending beyond said end of the opening nearest Ato the movable Contact, and each of the spherical surfaces titting into the ball holder with a press tit.

17. The switch described in claim 15 characterized by the movable contact being connected with the movable wall by a connection that gives the movable contact rocking movement in addition to its axial movement, the rocking movement including a rocking about the point of contact of the movable element with the spherical surface which it touches first whereby the first contact point of the movable element with one spherical surface acts as a fulcrum as the movable element rocks into contact with another of the spherical surfaces. v

118.7The switch described in claim 14 characterized by the spherical surface holder being made of electrical insulating material, the different spherical surfaces being located in separate openings in the holder, each of said openings having one end facing toward the end of the holder remote from the movable wall, a washer of electrical insulating material over the spherical surfaces but with openings exposing a portion of the surfaces of different spherical surfaces, the openings being at different radial distances from the axis of the switch, helical spring conductors, in the switch chamber, the spring conductors being of different diameter and substantially coaxial, and the smaller of the spring conductors being located within the other spring conductor, a sleeve of insulating material between the spring conductors, one of said spring conductors contacting with the exposed surfaces of one spherical surface and the other of said spring conductors contacting with the exposed surface of a different spherical surface, an insulation plug closing the upper end of the housing, prongs extending through the insulation plug, one of the prongs being connected with the other of the spring conductors.

I19. A fluid wave-responsive switch including a housing, a movable wall dividing the interior of the housing into two chambers including a switch chamber and a pressure chamber, an inlet passage for supplying fluid under pressure to said pressure chamber, an outlet passage from which uid escapes from the pressure chamber at a predetermined rate when the outlet passage is unobstructed, a switch in the switch chamber including relatively xed and movable contact means, the latter being operably connected with the movable wall, a holder for the fixed contact means, and resilient means urging movement of the movable Contact means and wall in a direction opposite to that in which the wall is moved by pressure in said pressure chamber, the movable contact means including a rearward portion that is secured to the movable wall and a forward portion that touches the relatively lfixed contact means to close the switch, the forward portion being slidable on the rearward portion transversely of the direction of movement of the contact means to open and close the switch, and the resilient means including a spring that gives the forward portion a bias toward a centered position with respect to the spring.

20. The switch described in claim 19` characterized by the rearward portion of the movable contact means being of composite construction and including a cup that is secured to a center area of the movable wall, and a disc of slippery material held in the cup and extending above the lip of the cup into contact with the back of the forward portion of the movable element, the front face of said forward portion having a center recess therein, and

the spring that gives the forward portion a bias being conical and having one end located in the recess and the other end held by the holder for the iixed contact means, and the spring having a substantially uniform pressure for both open and closed positions of the switch including closed positions of the switch after wear of the contacts.

21. A lluid wave-responsive switch including a housing, a movable wall dividing the interior of the housing into two chambers including a switch chamber and a pressure chamber, an inlet passage for supplying uid under pressure to said pressure chamber, an outlet passage from which fluid escapes from the pressure chamber at a predetermined rate when the outlet passage is unobstructed, a switch in the switch chamber including relatively fixed and movable contact means, the latter being operably connected with the movable wall, and resilient means urging movement of the movable contact means and wall in a direction opposite to that in which the wall is moved by pressure in said pressure chamber, the movable wall being a ilexible diaphragm, a shoulder in the housing, means clamping the peripheral portion of the diaphragm against the shoulder, the movable contact means including a portion connected with the diaphragm and covering a center area of the diaphragm radially spaced from the clamped edges of the diaphragm so as to leave an annular area facing the inside of the switch chamber, and a flexible washer impervious to ozone and covering the area of the diaphragm facing the inside of the switch chamber for protecting the diaphragm from ozone generated by any sparking within the switch chamber.

References Cited UNITED STATES PATENTS 1,065,576 `6/1913 Amet 200-46 XR 2,104,632 1/1938 Agnew 200-83 2,251,180 7/1941 Wesley et al ZOO-83 XR 2,438,512 3/1948 Mehut 200-83 2,675,827 4/ 1954 Craddock 20G- 61.86 3,093,716 6/ 1963 Horowitz 200-83 ROBERT K. SCHAEFER, Primary Examiner. H. BURKS, Assistant Examiner.

U.S. Cl. X. R. 

